This invention relates to motor vehicle tanks having a tank filling tube and a venting system connected to an upper portion of the tank filling tube.
Modern motor vehicle tanks for liquid fuels, in particular vaporizable fuels, have tight tank closures to prevent emission of vapors from the fuel tank and provide special venting system. Such tank venting systems are operative when the tank filling tube is closed. Ordinarily, the venting systems pass vent tank vapors to an active carbon filter which adsorbs fuel vaporized from the tank especially when the vehicle is stationary (e.g., due to heating of the contents of the tank, for example, by solar irradiation) so that no fuel vapors from the tank can escape into the environment. During filling of the tank, the venting system is usually shut off, i.e., is substantially closed, to provide a degree of venting of the tank which corresponds to a refill venting arrangement. Also, filling of the tank is stopped before the tank is completely filled so that, upon expansion of the fuel in the tank due to higher ambient temperature, the vehicle tank will not overflow.
During filling such a motor vehicle tank, the problem arises that fuel vapors present in the tank may escape into the environment. To avoid this, the fuel vapors from the tank may, for example, be captured with a fuel pump filling nozzle having vapor aspiration. But, such filling nozzles are not available everywhere.